<?php

interface Logger
{
    public function log(string $msg);
}

class Application
{
    private $logger;

    public function getLogger(): Logger
    {
        return $this->logger;
    }

    public function setLogger(Logger $logger)
    {
        $this->logger = $logger;
    }
}

$app = new  Application();
// 使用 new class 创建匿名类
$app->setLogger(new class implements Logger
{
    public function log(string $msg)
    {
        print($msg);
    }
});

$app->getLogger()->log("我的第一条日志");